1. Field
The present invention relates to a nitride semiconductor light emitting device, and more particularly, to a nitride semiconductor light emitting device capable of minimizing a decrease in light-emission efficiency at high currents.
2. Description of the Related Art
A semiconductor light emitting diode (LED) is a semiconductor device that can emit light of various colors due to electron-hole recombination occurring at a p-n junction when a current is applied thereto. Compared to conventional lighting sources such as incandescent lighting bulbs and fluorescent lamps, LED has many advantages such as a long lifespan, low power, excellent initial-operation characteristics, and high tolerance to repetitive power on/off. Hence the demand for LED is continuously increasing. Particularly, group III nitride semiconductors that can emit light in the blue/short wavelength region have recently drawn much attention.
As shown in FIG. 1, a group III nitride semiconductor light emitting device has high efficiency at low currents. However, at high currents, a significant decrease in quantum efficiency, which is called efficiency droop, occurs in the group III nitride semiconductor light emitting device. The efficiency droop is becoming a more crucial limitation as LEDs are increasingly used at high currents as in lighting devices. However, no methods have been proposed to completely solve this limitation associated with the efficiency droop. Therefore, there is a need for a high-efficiency nitride semiconductor light emitting device that achieves high quantum efficiency even at high currents and thus is applicable to a lighting device or the like.